This invention relates to textile pigment printing, and in particular to the production of a printed textile fabric wherein the printed areas are characterized by being substantially opaque and thus unaffected by the color of the underlying yarns.
Textile pigment printing, by definition, involves the printing of an insoluble coloring material (pigment) on selected areas of a textile fabric. The pigment, which has no affinity for the fibers of the fabric, is adhered to the fabric by a resin binder. The term "resin-bonded pigment" is often applied to this type of textile printing process and product.
In conventional textile pigment printing operations, the pigment colorants and resin binder are in an aqueous emulsion in the form of a thick printing paste, and this printing paste is applied to the fabric by patterned rollers or by screens. After the paste is printed onto the fabric, the fabric is subjected to heat to dry and cure the resin binder.
In conventional resin-bonded pigment prints of this type, the printed areas are relatively transparent. While the pigments serve to color the yarns, the underlying color of the yarn shows through. For this reason, pigment printing is usually done on an uncolored or white fabric. When pigment printing is done on predyed fabrics, it is generally restricted to the printing of darker colors over a lighter background color. Even then, the effect of the background color on the pigment must be taken into account in order to obtain the desired resulting color. For example, the printing of a blue pigment over a yellow background fabric will result in a greenish appearance as a result of the additive effect of the yellow and blue colors. Consequently, only limited colors can be otained by overprinting on predyed fabrics using conventional pigment printing techniques.
Attempts to overcome the effect of the background color by laying down a thicker layer of the aqueous printing paste have been generally unsuccessful. When the printing paste is applied to the fabric in a thick layer sufficient to completely cover and hide the underlying yarns and the fabric is dried and cured, the surface portions of the printed area dry first and form a skin which prevents evaporation of the moisture from the printing paste. This leads to an inadequately cured product or to an unacceptable mud-cracked appearance or both. Such products also have poor washfastness properties.
There are many textile designs and patterns which call for relatively small areas of a lighter color against a darker background color. To produce such patterns by conventional pigment printing techniques has required that both the lighter colored areas and the darker background areas be produced by printing onto an uncolored fabric. Consequently, the entire surface of the fabric is covered with resinbonded pigments. Such fabrics tend to have a relatively stiff, harsh hand and the colorfastness is not as great as in dyed fabrics. While this type of fabric is suitable for certain applications, such as for certain types of upholstery fabrics for example, it has limited applicability in other areas, such as for apparel fabrics, for example.
Because of the limited ability of conventional pigment printing techniques to produce the above-noted types of designs and patterns, a specialized process and apparatus has been developed which is capable of printing very opaque light or dark colors on fabrics, either undyed or predyed. This process and apparatus has been used commercially, for example, for printing a specialty fabric having a pattern of opaque dots resembling the appearance of a Jacquard-woven Swiss dot fabric. This technique utilizes a pigmented solvent-based lacquer, not unlike a paint, which is applied to the fabric in a relatively thick layer with a special type of rotary stencil printing range utilizing a perforated roll having the desired dot pattern. The perforated roll is costly and thus limits the number of patterns which can be produced. Because the printing paste is solvent-based, this process and apparatus requires an explosion-proof curing oven and a relatively expensive solvent recovery system for recovering the volatile solvent and maintaining acceptable air quality standards. To avoid bleeding of the dye from the fabric into the printed area and to assure safety of the process, the fabric must be cured at a relatively low temperature. Consequently, the apparatus has a relatively slow processing speed. Additionally, the apparatus is limited to only a single printing station, thus permitting only a single color to be printed on the fabric. Cleaning of the apparatus is very difficult and time consuming and requires the use of a volatile solvent. In fabrics produced by this process and apparatus, the lacquer dots or printed areas have exhibited a tendency to wear off, or to smear or run when contacted by certain chemicals contained in toiletries. Additionally, if such fabrics are ironed with too hot an iron, the lacquer dots may stick to the iron and/or discolor.
With the foregoing in mind, it is an object of this invention to provide a method for printing very opaque colors on textile fabrics using resin-bonded pigments, and wherein the limitations and disadvantages of conventional pigment printing and the aforementioned lacquer printing techniques are overcome.
It is a further object of this invention to provide a method for producing resin-bonded pigment printed fabrics in a wide variety of patterns and colors not obtainable by the printing techniques heretofore available.